There are items like the Bracers of Archery (levels 6, 16, 26) that are actually better than any feats you can pick at the same level (giving +2, 4, 6 to bow/xbow damage rolls, as opposed to +1/2/3 from Weapon Focus, or even +2/3/4 from a racial feat), so a single parcel seems about right, considering the player also has the freedom to choose which feat they'd like. The rule of thumb is that players should gain items above their level from the DM (DM's choosing of item), while gaining items below their level from enchanting/forging/alchemy (player's choosing of item), so a single feat for a single player (of the player's choosing) would make sense as a treasure parcel.

Personally, I've only given out feats as rewards a single time, and I picked the feats for the various characters at that time, since it fit the plot (as a thanks from the Raven Queen, she allowed one of her followers to pluck out a strand of a timeline that might have been, and then give it to the players).However, I counted giving one feat to each of the four players at that time as a single treasure parcel. They were feats that the players themselves wouldn't have thought of because of feat economization, but which added flavor (like the vampire/paladin hybrid gaining the Vampire bloodline, and the paladin/warlock hybrid gaining the Vistani heritage, since he had already been in a Vistani Blooding earlier). They all seemed very happy with their bonus feats.

..I do not know about 4th edition but I do that alot in my campaigns....

say for instance the first leg of the quest deals with alot of poison, or disease; in conjuction with xp and tang, uh.. tangi.... uh real magic items I would give each player say +2 fort save vs poison..

..now ive never handed out a feat, buuuut my first inclination is to say, make it pretty valuable.. ..feats build off each other, giving a PC a low level feat may give them access to a feat 3, 6 levels faster than their class and race would otherwise gain access to it.. ..feats can not be taken or destroyed or stopped..

..I gots to tell ya, if I was playing in your campaing and I got a feat as a reward, I would be pretty stoked...

A little nonsense now and then is relished by the wisest men.
- Willy Wonka

It greatly depends on the feat in question. As others have said, the first step is looking at similar items. It is never a 1-on-1 comparison though, since items give item bonusses, tend to take up a slot (you can have only a max number of items active at the same time) and items can theoretically be removed/destroyed. Unless your campaign regularly involves imprisonment, and/or infiltration into areas where magic items would draw a lot of attention, I wouldn't worry about the fact that items can be removed (especially not in 4e that virtually lacks item destruction powers and monster abilities). Slots and stacking is something you do need to take into account though.

For example, Skill Focus gives a +3 feat bonus on a single skill. The first time an item gives a similar bonus is around level 11, but it is item bonus and virtually always a specific slot. For example, skills such as Bluff, Diplomacy, Insight, Intimidate, Knowledges and Perception are tied to the head slot and few (if any items) give a bonus to all these skills as such a PC needs to select two or three of these skills that they want to give a boost. The feat lacks this limitation.

Of course, if you hand out feats as a reward, you have full control over it, and simply assigning it the level 14 item value is fine as long as you keep an eye on stacking. The +3 bonus is probably worth that amount of gold, but getting the +3 on 6 skills is not ;)

The rules in the DMG II for Reward-based games specifically says to remove the highest level and the lowest level magic item from the list of treasure parcels. That's all you need to worry about. Once you've done that (Hell, the highest level item is usually level+4 or +5) you've taken so much power out of the list of treasure parcels that I'd argue your free to do almost anything you want. You've given yourself a lot of room to move around, a lot of flexibility.

I run a low magic campaign, too. Once my players have taken their first multiclass feat, I give them powers from that class as Rewards, or Grandmaster Training, which is essentially a feat, though even a little more powerful since they aren't swapping powers for it. Or, I'll give them extra powers from their class, like if they want one of the more defensive Dailies but don't want to pass on the good offensive ones. As long as I dole out the medium level magic items to the other PCs I find that everything stay's pretty balanced.

One thing to consider is that instead of offering actual feats, offer additional backgrounds. They're typically not overly mechanically powerful, and can pack a lot of fluff to help round out a character's back story.

I sometimes wish there were specific non-combat feat slots alongside the typical feat selection. Something that boosts skills or things like movement modes. I mean, who's really going to blow a feat on something like a swim speed, or an additional language, or a specific bonus against one type of creature or terrain. Things that are usually totally dependent on what the DM puts you up against, but might be fun to have nonetheless.